The sequence specific suppression of HIV-1 replication using CD4-antibody-targeted liposomes containing antisense phosphorothioate oligonucleotides is described. Liposomes were generated encapsulating the 20-mer antisense DNA sequence of the rev HIV-1 regulatory gene in the form of a phosphorothioate oligonucleotide. Specific targeting was accomplished by conjugating anti human CD4 monoclonal antibody to the surface of the liposomes. HIV-1-infected H9 cells incubated with the immunoliposomes were rendered less permissive for viral multiplication in comparison with the positive control. HIV-1 replication was reduced by 80 percent in antisense immunoliposome treated cells. Inhibition of HIV-1 replication was not observed using empty immunoliposomes or immunoliposomes containing scrambled rev phosphorothioate oligomer sequences. These immunoliposomes exhibit dual specificity because of a targeting antibody on the surface of the liposome specific for infected cells, and an oligomer inside the immunoliposome that is complimentary to a specific portion of the mRNA of the infected cell. The antiviral activity of both the free and the encapsulated oligonucleotides were assessed by p24 assay, RT assay, and PCR analysis. Liposome preparations demonstrated minimal toxicity in H9 cell culture experiments. These in vitro culture results demonstrate the potential efficacy of drug-encapsulating immunoliposomes in the treatment of AIDS and AIDS related infections.